1. Field of the Invention
The present invention generally relates to implantable devices, and in particular to an implantable electric lead.
2. Description of the Prior Art
Various types of body-implantable electric leads are known and used in the medical field. For example, implantable medical devices, IMDs, such as pacemakers, cardiac defibrillators and cardioverters are, in operation, connected to implantable electric leads for sensing cardiac function and other diagnostic parameters and delivering stimulation pulses. For example, endocardial electric leads are attached at their proximal end to an IMD and at their distal end to the endocardium of a cardiac chamber.
In the art, multipolar leads comprise at least two electrodes in connection with their distal portion to be provided attached or close to the sensed and/or stimulated tissue. Consequently, these multipolar leads comprise at least two conductors running in the lumen of the lead body to electrically connect the electrodes with the IMD during operation. The conductors may be in the form of coils coaxially arranged in the lumen and electrically isolated from each other by an insulating sheath or tubing. This insulating tubing is attached, in the proximal portion of the lead, to a so-called connector coupling, which in turn is mechanically connected to a connector ring electrically connected to the outer conductor. When handling the implantable electric lead during implantation, the connector coupling and connector ring can be caused to rotate relative each other. Such unintentional rotation also rotates the insulating tubing, leading to a significant risk of breaks in the insulating tubing. The breaks in the insulating tubing will cause the implantable electric lead to short circuit between the two conductors, thereby preventing correct operation of the implantable electric lead and the IMD to which it should be connected.